1. Field of the Invention
This invention relates to a binocular stereoscopic observation apparatus, an electronic image stereomicroscope, an electronic image stereoscopic observation apparatus, and an electronic image observation apparatus that are suitable for the application of work to an object to be observed.
2. Description of Related Art
In conventional practice, a stereomicroscope has been used to perform a surgical operation under a microscope that requires processing work of minute portions and accurate work in a narrow region on the periphery of an affected part. Recently, it has been desired that such work should be carried out by remote control. This is because if the work can be carried out by remote control, the work and the surgical operation can be performed at various places without moving work engineers and surgeons of high order. In order to realize such remote control, it is necessary to electronize an observation image in the stereomicroscope.
Most of commonly used stereoscopic imaging apparatuses are designed so that stereoscopic observations can be made by using binocular parallax that two images with parallax are formed in an imaging section and are observed with the eyes in an observing section. A stereoscopic image obtained by observing such two images with parallax through the eyes is called a “stereo image” in the present invention. In such a stereoscopic imaging apparatus, when the depth of the optical system of the imaging section is enlarged, resolution is impaired, while when an aperture is increased to improve the resolution, the depth of the optical system of the imaging section becomes small. However, the work engineer or surgeon of high order, who observes an optical image, is capable of widening a focus adjusting region by the accommodation of the eye even when the aperture is increased to improve the resolution and the depth of the optical system of the imaging section becomes small. Consequently, in a conventional stereoscopic imaging apparatus, the depth of the optical system is small in the same resolution, but the focusing region of the optical image is widened.
In such a stereo image, it is known that a simple portion corresponding to the two images with parallax (for example, the contour of an object) is good in image reproducibility, but a portion, such as swelling of a smooth object, is bad in reproducibility in the direction of the line of sight. This is called a cardboard effect, and an image largely manifesting this effect appears to be a depth-free image such that a picture is drawn on a flat plate.
Apparatuses and methods for super multiocular observation and hologram in which image information in the direction of the line of sight is obtained have been proposed. Depth-fused three dimensional apparatuses and methods are proposed, for example, in Japanese Patent Kokai Nos. 2000-214413 and 2000-341473.
Kokai No. 2000-214413 discloses that the density of each of a plurality of images arranged in the direction of the line of sight is changed and thereby positions between the plurality of images can be represented. Kokai No. 2000-341473 discloses that blurred images spaced along the optical axis are formed and superimposed for display and thereby information in the direction of the optical axis is obtained and can be recognized as a stereoscopic image.
In general, it has been considered that even when the images are superimposed as mentioned above, the presence of a plurality of images is merely recognized as cardboard-like images. Since it has been assumed that the presence of the blurred images causes image degradation such as a reduction in contrast, processing for eliminating blurred portions has been performed.
However, when the blurred images are actually superimposed in the direction of the line of sight and are observed, they are not recognized and look like a natural stereoscopic image that has no cardboard effect. It is for this reason that the images are arranged in the direction of the line of sight, thereby affording a view similar to a change of the optical image obtained when a focus is altered.
From this, it is considered that a person recognizes an image by a plurality of points with respect to information in the direction of the line of sight and perceives a change in contrast of the image (a change in density of the image) as stereoscopic information. In particular, when at least two images are specified by the parallax of the eyes with respect to their positions, the effect of the stereoscopic image is brought about.
In the case where the stereoscopic image is formed by this technique, the effects of binocular parallax, motion parallax, vergence, and accommodation (the focus adjustment of the eyes) are produced little by little, so that a natural stereoscopic image is obtained and eye strain is relieved accordingly.